This invention relates to a one-piece blind nut, and more particularly, to an improved one-piece blind nut for flush attachment to a workpiece wherein the blind nut includes a clearance chamber which receives the metal which flows during the installation of the nut to the workpiece.
Fasteners of the class commonly known as "blind fasteners" or blind nuts are known and are utilized to assemble various elements together, the term "blind fastener" generally being used to describe a fastener which can be assembled from one side of the work. Typical of the uses of the blind fasteners or blind nuts are attachment of cover plates, name plates, decorative panels, skin panels, and the like.
In general, these blind fasteners or blind nuts are collapsed to secure them to the workpiece, and optimally, once installed, the blind nut does not rotate with respect to the workpiece.
In many applications, it is desired that the blind nut be installed flush with respect to the workpiece. In some blind nuts of the prior art, it has been necessary to provide an aperture in the workpiece which must be provided with a countersink for installation of the blind nut. The countersinking operation is a second operation and therefore increases the time and expense incident to the use of blind nuts which require countersinking of the work piece in order for their use.
Typical of the prior art blind fasteners are those described in U.S. Pat. Nos. 2,324,142; 3,136,203; 3,236,143; 3,322,449; 3,369,442; and 3,657,955.
While the above-identified structures operate satisfactorily, in some instances there is objection because of the need to provide a countersunk aperture in the workpiece, or, in the alternative, the expense in manufacturing the blind nut is a serious consideration. For example, any blind nut structure that is composed of multiple pieces requires an assembly operation during their manufacture which has the effect of increasing the unit cost of each such blind nut.
In addition to blind nuts of the types illustrated in the above patent, there is commercially available a blind nut formed of a single piece construction, the blind nut having a generally cylindrical bore which terminates at one end in a tapered section, the external configuration of the blind nut being such that it includes a narrow band at one end which is serrated. There is a groove near the serrated end and adjacent to the groove is an enlarged section which is received within the aperture in the workpiece. The portion of the bore between the enlarged section which is received in the aperture and the threaded end is of a tapered configuration such that as the nut is collapsed through the use of anvil and a mandrel, metal flows radially outwardly to form a locking key. The objection to the above type of blind nut is the fact that the preparation of the aperture requires a countersinking operation which adds to the cost of installation during use of the nut.
Accordingly, it becomes apparent that there are advantages from a cost standpoint of being able to provide a blind nut fastening type device which is of a one piece structure. The reduction in manufacturing costs results in a reduction in the unit cost of the nut. Moreover, the provision of a fastener which is of a single piece structure and which may be received within an aperture which does not include a countersunk portion is quite desirable. The advantages of such a structure are the savings in the cost of the manufacture and the savings in the cost of installation, each a practical advantage of some significance.
It would also be of advantage to provide a blind fastener type of structure in which the fastener may be used with workpieces of different cross-sectional dimensions, that is, one nut which may be used with a series of workpieces which vary in cross-sectional dimension over a range.